An empty glass turned upside down is actually not empty. It is full of _____.
John and Sam were playing with empty bottles, John took an empty plastic bottle, turned it upside down and dipped its open mouth into a bucket filled with water. He then tilted the bottle slightly and made the following observations.
(i)Water did not enter the bottle when it was in inverted position. (ii)Bubbles of air came out from the bottle as soon as it was tilted. (iii)Some water entered the bottle (iv)No bubbles formed, only water entered the bottle.
Which observations is/are correct?
It is easy to push an empty box than a same box full of books, because _____.